The invention relates generally to a carrier vehicle with a moveable bed which is maneuverable to load and unload other vehicles, such as disabled cars, racing vehicles, etc. More specifically, the invention concerns an arrangement for preventing inadvertent tilting of the moveable bed when the bed is engaging a hold-down device associated with the carrier vehicle frame.
Typical known vehicle carriers with which this invention is concerned provide a positive lock-down element which engages the moveable carrier bed as it slides forward into its normal position to maintain the bed in its load carrying orientation. In such systems however, users have experienced problems with personnel forgetting that the carrier bed has been engaged by the lock-down element and proceeding to engage the vehicle's hydraulic system to begin tilting of the bed thereby causing damage to the lock-down device and to the truck chassis itself. Known solutions to preventing this problem by providing a tilt lock-out arrangement have used a mechanical means to physically prevent a lever or crank associated with the hydraulic tilt control system from being physically actuated. One such known arrangement is disclosed in U.S. Pat. No. 4,756,658 to Moore et al. Moore utilizes a mechanical stop-plate secured to the carrier bed in conjunction with a cam element coupled to a linkage control rod of the hydraulic actuator system. The stop-plate is disposed such that when engaged by the cam, the cam, and thus the control rod are precluded from turning thereby inhibiting the passage of a tilt command to the hydraulic system which, in turn, prevents tilting of the carrier bed.
Other known tilt lock-out arrangements utilize moveable contacts of a limit switch with a probe positioned to detect the position of the carrier bed and in accordance with that position to either inhibit or allow hydraulic fluid flow to a tilt control cylinder at preselected longitudinal positions of the carrier bed.